Vehicle security systems are widely used to deter vehicle theft, prevent theft of valuables from a vehicle, deter vandalism, and to protect vehicle owners and occupants. A typical automobile security system, for example, includes a central processor or controller connected to a plurality of vehicle sensors. The sensors, for example, may detect opening of the trunk, hood, doors, windows, and also movement of the vehicle or within the vehicle. Ultrasonic and microwave motion detectors, vibration sensors, sound discriminators, differential pressure sensors, and switches may be used as sensors. In addition, radar sensors may be used to monitor the area proximate the vehicle.
The controller typically operates to give an alarm indication in the event of triggering of a vehicle sensor. The alarm indication may typically be a flashing of the lights and/or the sounding of the vehicle horn or a siren. In addition, the vehicle fuel supply and/or ignition power may be selectively disabled based upon an alarm condition.
A typical security system also includes a receiver associated with the controller that cooperates with one or more remote transmitters typically carried by the user as disclosed, for example, in U.S. Pat. No. 4,383,242 to Sassover et al. The remote transmitter may be used to arm and disarm the vehicle security system or provide other remote control features from a predetermined range away from the vehicle.
A typical vehicle security system issues one or more audible "chirps" to confirm certain operations to the user. For example, when a user leaves his vehicle and presses the arm button on the remote transmitter, the vehicle controller will typically cause a siren or horn to sound one or more chirps. The chirps confirm that the user has properly armed the vehicle. Similarly, upon returning to the vehicle, the user may press a disarm button on the remote transmitter and two chirps are sounded, thereby indicating that the vehicle security system has been disarmed.
Unfortunately, although the chirps serve a useful purpose to the vehicle owner, the chirps may be intrusive to others in the area. This is especially so since the pattern of chirps is typically generated by the horn or siren at the full power of the alarm indication, but for a reduced duration. This disadvantage becomes more prominent as areas become more highly populated, and more and more vehicles have security systems.
U.S. Pat. No. 5,534,845 to Issa et al. discloses a vehicle security system where the chirps may be turned completely off, and a visual only indication is provided to confirm that a command has been received from the remote transmitter. In other words, this patent describes a chirp elimination feature to avoid the annoyance or nuisance as may be caused by full volume confirmation chirps from a vehicle security system.
Yet another approach to the potential annoyance caused by confirmation chirps is provided by allowing the user to select a reduced volume or "soft chirp" for confirmation signals. A vehicle security system including such a soft chirp feature is disclosed, for example, in U.S. Pat. No. 5,572,185 to Chen et al.
The drawbacks with the visual only confirmation signals and soft chirp signals is that the user may not be assured that the desired command signal has been received by the vehicle security system, and carried out. The user may not see a visual only confirmation signal depending on other potentially intervening objects and/or the distance from the vehicle. The soft chirp may not be heard if the distance to the user is too far or ambient noise is too great. Accordingly, neither the visual only or soft chirp approaches are wholly satisfactory from the user's perspective. Indeed, since the user may repeatedly activate the remote transmitter if he cannot see or hear confirmation, the visual only and soft chirp features may lead to more annoyance than a conventional system producing full volume chirp confirmation signals.